Was watching G4 last night and they mentioned this:
This means that major sites like Youtube, Google, Facebook, Amazon, etc. will be shut down to protest SOPA the day before the bill's final hearing date, hopefully making the government reconsider. A blackout protest like this would be huge, I'd love to see it go down in history.However, as the final hearing date for SOPA approaches, tech giants like Google, Facebook, Amazon and Twitter have decided to join hands to bring out a deadly weapon from their arsenal. All these tech giants are part of the Net Coalition group, and they have decided to blackout their homepages with anti-censorship warnings, urging users to contact their representatives in the government.
For more information, take a look at this article: Tech Giants Consider a Massive Blackout in Protest